【单选题】【消耗次数：1】
Have you remembered _______the windows? It’s going to rain.
①
locked
②
to lock
③
locking
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相关题目
【单选题】
It is going to rain. The sky is getting _________ and ________.
①
dark, dark
②
darker and darker
③
darkest and darkest
④
dark and darker
【单选题】
9. -You’d better not go out now. It’s raining. -It doesn’t matter. My new coat can keep ______ rain.
①
in
②
of
③
with
④
off
【单选题】
Im going to the supermarket this afternoon. Do you have anything ____?
①
to be buying
②
bought
③
for buying
④
to buy
【单选题】
We are going to have a singing party tonight. Would you like to join us?___________
①
I’m afraid not, because I have to go to an important meeting.
②
Of course not. I have no idea.
③
No, I can’t.
④
That’s all set.
【单选题】
We are going to have a dancing party tonight. Would you like to join us?
①
I’m afraid not. Because I have an appointment with my dentist tonight
②
Of course not. I have no idea
③
No, I can’t
④
That’s all set
【单选题】
The sports meeting was put off till the next week ______ rain.
①
in spite of
②
so
③
because
④
because of
【单选题】
_____ that it was going to rain, he took a raincoat with him.
①
Seeing
②
Saw
③
Seen
④
To see
随机题目
【单选题】
关于线性系统稳定性的判定，下列观点正确的是（）。
①
线性系统稳定的充分必要条件是：系统闭环特征方程的各项系数都为正数；
②
无论是开环极点或是闭环极点处于右半S平面，系统不稳定；
③
如果系统闭环系统特征方程某项系数为负数，系统不稳定；
④
当系统的相角裕度大于零，幅值裕度大于1时，系统不稳定。
【单选题】
关于系统频域校正，下列观点错误的是（）
①
一个设计良好的系统，相角裕度应为45度左右；
②
开环频率特性，在中频段对数幅频特性斜率应为；
③
低频段，系统的开环增益主要由系统动态性能要求决定；
④
利用超前网络进行串联校正，是利用超前网络的相角超前特性。
【单选题】
采用负反馈形式连接后，则（）
①
一定能使闭环系统稳定；
②
系统动态性能一定会提高；
③
一定能使干扰引起的误差逐渐减小，最后完全消除；
④
需要调整系统的结构参数，才能改善系统性能。